Naive code to indent HTML for readability

index.js

var myHtml = `<div billing-total="" quote="quote" payment-frequency="frequency" on-select-frequency="onSelect(frequency)" payment-plan="plan" class="ng-scope ng-isolate-scope"><div class="billing-frequency-wrap container"><div class="billing-total col col-lg-3 col-md-3 col-sm-8 col-xs-4"><div class="frequency"><div class="freq-select"><div class="mdl-textfield mdl-js-textfield mdl-textfield--floating-label getmdl-select text-input"><label for="paymentFrequency" class="mdl-textfield-label-right"><i class="material-icons filled">done</i> <i class="mdl-icon-toggle__label material-icons">arrow_drop_down</i></label><span><i class="material-icons filled">done</i></span> <input class="mdl-textfield__input" type="text" id="paymentFrequency" placeholder="Monthly" readonly="readonly" value=""><label for="paymentFrequency" class="mdl-textfield__label"><span>Billing Frequency</span></label><div class="getmdl-select-container" ng-click="setPaymentFrequency($event);"><ul for="paymentFrequency" class="mdl-menu mdl-js-menu mdl-menu--bottom-left"><!-- ngRepeat: planObj in paymentPlans --></ul></div></div><span class="prcnt-off ng-binding"></span></div></div><div class="todays-total" ng-class="{'breakdown-showing':showPaymentBreakdown}"><ul class="billing-breakdown"><!-- ngRepeat: item in paymentPlans[checkoutData.paymentFrequency].items --></ul><div class="grand-total"><div class="todays-total-title"><span class="word-break">Today's</span> Total</div><h2 class="total-price ng-binding">$0.00</h2></div><div class="billing-breakdown-show-breakdown billing-frequency-toggle" ng-click="showPaymentBreakdown = !showPaymentBreakdown">SEE PAYMENT BREAKDOWN</div><div class="billing-breakdown-show-less billing-frequency-toggle" ng-click="showPaymentBreakdown = !showPaymentBreakdown">SEE LESS</div></div></div></div></div>`;
var args = myHtml.trim().split('<').slice(1).map((a)=> '<' + a + '\n');
var indent = 0;
args = args.map((a)=>{
  console.log('a is',a, indent, a.indexOf('</'));
  if ( a.indexOf('</') === 0){
    console.log('found closing');
    indent = indent - 4;
    return new Array(indent).join(' ') + a
  } else if ( a.indexOf('<!') === 0 || a.indexOf('<input') === 0){
    return new Array(indent).join(' ') +  a;
  }else{
    var result =  new Array(indent).join(' ') + a;
    if ( a.slice(a.length-2) !== '/>'){          indent += 4; }
    return result;
  }
})
console.log(args.join(''));//  ==> should print formatted html